Dormancy

You learned in module 1 that some seeds may not germinate because they are dormant. These dormant seeds are operating on minimum metabolism, and even if environmental conditions are favorable, something else needs to happen to break their dormancy.

Dormancy can have an impact on perceived viability. If you expect viability to tail off over time in an S-shaped curve, the viability of a brand new, fresh batch of certain types of seeds can appear a little disappointing. This is because dormancy prevents some seeds from germinating, creating a false impression that they are not viable, when in fact they may just be dormant. This is common in wild species, where dormancy is a functional response to the problems of living in situ. It may prevent tender young seedlings from emerging during seasons when conditions are at their harshest. Even in an ex situ genebank setting, it is important to be alert to the possibility of dormancy.

Figure 9 shows how the changes in germination rate over time may look for a species that exhibits dormancy:

Figure 9: effect of dormancy on longevity

Later in this course, you will find out more about the mechanisms behind dormancy and discover ways of breaking it. But at the moment, it is worth noting that it is possible for dormancy to mask the true viability of a seed lot.